Detecting an object from an underwater vehicle is usually a difficult task because both the direction (bearing) and also the distance must be determined. The further away the object to be detected, the greater effect that possible errors have on determining the direction angle (bearing angle).
Particularly with side-scan sonars (passive flank-array sonar or active side-scan sonar) which, for example, form a linear antenna, the linear antenna is rotated step-by-step electronically or under computer control, and the corresponding incoming signal strength determined. The angle with the greatest beam-formed signal strength corresponds to the direction angle on the basis of which a downstream range determination, for example, is made.
To reduce the error in determining the direction, the electronic rotation of the linear antenna can be performed with smaller step-widths. This does, however, have the drawback of considerably increasing the corresponding computing effort and of the results not being available within an acceptable time.
Consequently, a method must be provided by which the most accurate direction (bearing) possible can be determined within two measurement periods.